Cooled turbine assembly

Abstract

A gas turbine engine ( 10 ) is provided with a stage of turbine blades ( 22 ) surrounded by hollow shroud segments ( 28 ). Cooling of the shroud segments ( 28 ) is achieved by providing a flow of engine leakage air from space volume ( 48 ) centrally of the engine ( 10 ) via an annular compartment ( 46 ) wherein it is diverted away from the blade cooling system and passed via piping ( 44 ) within each guide vane ( 20 ) to shroud segments ( 28 ). The flow impingement cools the shroud segments ( 28 ) and then passes into the gas annulus via slots ( 60 ).

1. A cooled turbine structure comprising hollow shroud segments, at least one seal allowing air leakage, pipe members adjacent stages of guide vanes and turbine blades wherein said turbine blades are surrounded in spaced relationship by said hollow shroud segments that are connected via respective upstream ends to said guide vanes, said seal allowing air leakage through said seal to a central space volume wherein said air leakage is provided to cool said shroud segments, the passage of said air leakage from said central space volume to said hollow shroud segment interiors being enabled by said pipe members which extend through said guide vanes which connect said space volume and said hollow shroud segment interiors in flow series and wherein said shroud segments include air leakage exit apertures in their respective downstream edges. 
   
   
     2. A cooled turbine structure as claimed in  claim 1  wherein each hollow shroud segment interior includes a dividing wall so as to provide radially inner and outer compartments with respect to an axis of rotation of a gas turbine engine. 
   
   
     3. A cooled turbine structure as claimed in  claim 2  wherein said dividing wall has multiple perforations therein so as to enable air leakage to flow from one compartment to the other compartment. 
   
   
     4. A cooled turbine structure as claimed in  claim 3  wherein the direction of flow from one compartment to the other compartment is radially inward with respect to the axis of rotation of the gas turbine engine. 
   
   
     5. A cooled turbine structure as claimed in  claim 4  wherein said air leakage exit apertures connect said radially inward compartment with the gas annulus of the gas turbine engine. 
   
   
     6. A cooled turbine structure as claimed in  claim 2  wherein each said dividing wall is spaced from its associated inner wall by pillars. 
   
   
     7. A cooled turbine structure comprising hollow shroud segments, pipe members adjacent stages of guide vanes and turbine blades wherein said turbine blades are surrounded in spaced relationship by said hollow shroud segments that are connected via respective upstream ends to said guide vanes, leaked air from a central spaced volume in a gas turbine engine, the passage of said leaked air from said central space volume to said hollow shroud segment interiors being enabled by said pipe members which extend through said guide vanes which connect said space volume and said hollow shroud segment interiors in flow series and wherein said shroud segments include leaked air exit apertures in their respective downstream edges wherein the leaked air inlet end of each shroud segment is shaped so as to engage said pipe members by point contact only. 
   
   
     8. A cooled turbine structure as claimed in  claim 7  wherein the shroud segments are pivotal such that on extension of their respective guide vanes if exposed to excessive heat, said extension pivots said shroud segments away from the tips of their adjacent turbine blades. 
   
   
     9. A gas turbine engine including a cooled turbine structure as claimed in  claim 1 .